On a warm, sunny morning in September, a group of Class 8 students gathered on the roof to conduct an experiment in science that gave new meaning to the term “immersive.”
At the center of the activity was an extra-large grey rubber garbage can filled with water from a nearby hose. Completely submerged was one of their classmates, who had volunteered to take a dip to help solidify their understanding of density, the ratio of an object’s mass to its volume.
After changing into a T-shirt and shorts, the good-natured student carefully stepped into the bucket, taking great care not to cause any overflow. As the class witnessed, not spilling was a virtual impossibility, but it was also an opportunity for learning.
To generate proper data, the student was instructed to hold still and refrain from blowing bubbles once completely submerged. This took a few attempts and elicited giggles from the others. Despite the humorous set-up, the class handled their various tasks with curiosity and a seriousness of purpose.
“You’ll have to figure out how to collect and measure the water,” science teacher David Arnstein told the members of section X. (The other three sections, W, Y and Z, taught by Mr. Arnstein and Prasad Akaavor, completed the investigation at other times).
The further the student sank down, the higher the water level rose up. Although some liquid inevitably escaped over the top, the majority of the run-off was funneled through a pipe connected to the garbage bucket, which fed into a much smaller green bucket.
When the green bucket filled, a student plunged a plastic pitcher into the cool water, then worked with two classmates to decant the contents into several graduated cylinders. They examined the levels and reported the measurements to a record keeper, who sat nearby entering figures onto a spreadsheet. On a second laptop, another student noted the steps the class followed and various observations.
“Let’s try to calculate the volume,” said Mr. Arnstein, who is also Head of the Upper School Science Department. “Is it too high or too low? What do you think?”
“It was too low because she didn’t stay submerged,” one student suggested. “We were losing water,” another added on.
As the student climbed out of the bucket and went to dry off on the sun-soaked turf, Mr. Arnstein steered the class toward the overarching theme of the lesson: accuracy and precision of measurement. “Let’s think about the major sources of error in this lab,” he said.
After a quick brainstorm, a number of ideas came up, including: “We were moving too fast”; “We may have made mistakes reading the graduated cylinders” and “There was a lot of spilling.”
A previous discussion had introduced the students to the difference between these two concepts. In short, accuracy refers to how close a measurement is to the true or accepted value (for example, how close an arrow gets to the bull’s-eye center). By contrast, precision describes how close measurements of the same item are to each other (for example, how close a second arrow is to the first one).
Equipped with this knowledge, the students delved deeper into the nuances of accuracy and precision in the second portion of the period, which took place two floors down in the Athletic Training Room. Once again, Mr. Arnstein relied on students to play essential roles.
Using a yardstick, the class measured the two rectangular treatment tubs and the water height in each. Then, with the assistance of Head Athletic Trainer Ali Levy, a pair of volunteers got into the tubs – one warm and one cold – and lay unmoving below the water’s surface. The team measured the height of the water again and collected supplemental data, carefully recording their findings, which they would analyze in a later class.
As the volunteers toweled off and the other students finished up, the feeling in the room was energetic and collaborative. Without question, this immersive density experiment resonated with these young scientists, preparing them well for further explorations in Class 8 science.
